In recent years, there have been great advancements in the speed, power, and complexity of integrated circuits, such as application specific integrated circuit (ASIC) chips, random access memory (RAM) chips, microprocessor (uP) chips, and the like. These advancements have made possible the development of system-on-a-chip (SOC) devices. A SOC device integrates into a single chip all (or nearly all) of the components of a complex electronic system, such as a wireless receiver (i.e., cell phone, a television receiver, and the like). SOC devices greatly reduce the size, cost, and power consumption of the system.
Reductions in power consumption are particularly important in SOC designs. SOC devices are frequently used in portable devices that operate on battery power. Since maximizing battery life is a critical objective in a portable device, it is essential to minimize the power consumption of SOC devices that may be used in the portable device. Furthermore, even if an SOC device is not used in a portable device, minimizing power consumption is still an important objective. The increased use of a wide variety of electronic products by consumers and businesses has caused corresponding increases in the electrical utility bills of homeowners and business operators. The increased use of electronic products also is a major contributor to the increased electrical demand that has caused highly publicized power shortages in California.
To minimize power consumption in electronic devices, particularly SOC devices, many manufacturers have reduced the voltage levels at which electronic components operate. Low power integrated circuit (IC) technology operating at +3.3 volts replaced IC technology operating at +5.0 volts. The +3.3 volt IC technology was, in turn, replaced by +1.6 volt IC technology in many applications, particularly microprocessor and memory applications.
However, reducing power supply levels also reduces performance. High frequency operations require higher voltage levels in order to rapidly switch signal lines from high to low, and vice versa. This frequently results in wasted power if an integrated circuit does not always operate at high speed. For example, during a period when only a relatively low level of processing power is needed, a high performance circuit that operates at +3.3 volts or higher will consume more energy than needed. Unfortunately, if the circuit is operated at +1.6 volts, the circuit will not be able to provide high-speed performance when it is required. Thus, circuit designers are often forced to make tradeoffs between power consumption and performance when selecting the operating speed and power supply levels of a device.
Therefore, there is a need in the art for system-on-a-chip (SOC) devices and other large scale integrated circuit devices that are capable of operating at high frequencies while minimizing power consumption. In particular, there is a need for SOC devices and other IC devices that are capable of switching to a low power mode when high performance is not required. More particularly, there is a need for SOC devices and other IC devices that are capable of varying power supply voltage levels to reduce power consumption when high performance is not required.